U.S. patent application number 13/265611 was filed with the patent office on 2012-10-25 for screen printing apparatus and screen printing method.
This patent application is currently assigned to Panasonic Corporation. Invention is credited to Yuji Otake, Tetsuya Tanaka.
Application Number | 20120269959 13/265611 |
Document ID | / |
Family ID | 44672772 |
Filed Date | 2012-10-25 |
United States Patent
Application |
20120269959 |
Kind Code |
A1 |
Tanaka; Tetsuya ; et
al. |
October 25, 2012 |
SCREEN PRINTING APPARATUS AND SCREEN PRINTING METHOD
Abstract
There are provided a screen printing apparatus and a screen
printing method which can realize an increase in conversion
efficiency of a solar cell by forming a circuit pattern having a
large aspect ratio of a sectional shape by increasing the thickness
of the circuit pattern. A screen printing apparatus 10 and a screen
printing method for forming a belt-shaped circuit pattern on a
surface of a substrate 11 include a support table 12 which supports
the substrate, a metal mask 1 having a covering portion which
covers a part of the surface of the substrate 11, a plurality of
apertures from which a part of the substrate 11 is exposed and
bridge portions which are provided between the apertures along a
direction which intersects a longitudinal direction of a circuit
pattern to be formed and a cartridge-type squeegee head 13 which
supplies a paste which constitutes a circuit pattern to a surface
of the metal mask 1 under a predetermined pressure while causing a
squeegee 14 of a predetermined length to slide on an upper surface
of the metal mask 1 in a contact fashion.
Inventors: |
Tanaka; Tetsuya; (Yamanashi,
JP) ; Otake; Yuji; (Yamanashi, JP) |
Assignee: |
Panasonic Corporation
Osaka
JP
|
Family ID: |
44672772 |
Appl. No.: |
13/265611 |
Filed: |
March 18, 2011 |
PCT Filed: |
March 18, 2011 |
PCT NO: |
PCT/JP2011/001653 |
371 Date: |
October 21, 2011 |
Current U.S.
Class: |
427/98.4 ;
118/200 |
Current CPC
Class: |
B41F 15/46 20130101;
B41M 1/12 20130101; H01L 31/022425 20130101; H05K 3/1233 20130101;
B41N 1/24 20130101; B41F 15/36 20130101; B41F 15/423 20130101; B41F
15/0881 20130101; Y02E 10/50 20130101; B41P 2215/50 20130101 |
Class at
Publication: |
427/98.4 ;
118/200 |
International
Class: |
H05K 3/12 20060101
H05K003/12 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 24, 2010 |
JP |
2010-068254 |
Claims
1. A screen printing apparatus for forming a belt-shaped circuit
pattern on a surface of a substrate comprising: a support table for
supporting the substrate; a metal mask having a covering portion
for covering a part of the surface of the substrate, a plurality of
apertures from which a part of the substrate is exposed and bridge
portions provided individually between the apertures along a
direction which intersects a longitudinal direction of the circuit
patterns; and a cartridge-type squeegee head for supplying a paste
to be the circuit pattern to a surface of the metal mask under a
predetermined pressure while causing a squeegee of a predetermined
length to slide relatively on an upper surface of the metal mask in
a contact fashion.
2. The screen printing apparatus as set forth in claim 1, wherein a
lower surface of the bridge portion constitutes a depressed step
surface relative to a lower surface of the covering portion.
3. A screen printing method for forming a belt-shaped circuit
pattern on a surface of a substrate comprising the steps of:
causing the substrate to be supported on a support table; placing a
metal mask having a covering portion for covering part of the
surface of the substrate, a plurality of apertures from which part
of the substrate is exposed and bridge portions provided
individually between the apertures along a direction which
intersects a longitudinal direction of the circuit patterns on a
surface of the substrate; and then, supplying a paste to be the
circuit pattern to a surface of the metal mask under a
predetermined pressure by a cartridge-type squeegee head while
causing a squeegee of a predetermined length to slide relatively on
an upper surface of the metal mask in a contact fashion.
Description
TECHNICAL FIELD
[0001] The present invention relates to a screen printing apparatus
and a screen printing method for printing a paste such as a solder
paste or a conductive paste on a substrate and more particularly to
a screen printing apparatus and a screen printing method which are
applied in forming electrodes of a solar cell.
BACKGROUND ART
[0002] Conventionally, there have been known screen printing
apparatuses and screen printing methods which employ a mesh mask
for printing to form electrodes (refer to Patent Literature 1, for
example).
RELATED ART LITERATURE
Patent Literature
[0003] Patent Literature (PTL) 1: JP-A-2007-62079 (FIG. 1,
Paragraph 0052)
SUMMARY OF THE INVENTION
Problem that the Invention is to Solve
[0004] In order to increase the conversion efficiency of a solar
cell, it is effective to increase the light receiving area of the
solar cell by thinning electrodes thereof. However, a thinned
electrode increases extremely electrical resistance and calls for a
deterioration in performance, which decreases the conversion
efficiency on the contrary. Thus, the thickness of an electrode to
be printed needs to be increased.
[0005] In the screen printing apparatus and screen printing method
of PTL 1 above, however, a mesh provided in an opening portion in a
mesh screen constitutes resistance to thereby decrease the mesh
aperture, and therefore, the thickness of the printed electrode
formed by use of this mesh mask is thinned.
[0006] Consequently, there are fears that the conversion efficiency
of a solar cell which is produced by use of the screen printing
apparatus and the screen printing method of PTL 1 is decreased.
[0007] The invention has been made with a view to solving the
problem described above, and an object thereof is to provide a
screen printing apparatus and a screen printing method which can
realize an increase in conversion efficiency of a solar cell to be
produced by forming a circuit pattern having a large aspect ratio
of a sectional shape by increasing the thickness thereof.
Means for Solving the Problem
[0008] According to the invention, there is provided a screen
printing apparatus for forming a belt-shaped circuit pattern on a
surface of a substrate comprising: a support table for supporting
the substrate; a metal mask having a covering portion for covering
a part of the surface of the substrate, a plurality of apertures
from which a part of the substrate is exposed and bridge portions
provided individually between the apertures along a direction which
intersects a longitudinal direction of the circuit patterns; and a
cartridge-type squeegee head for supplying a paste to be the
circuit pattern to a surface of the metal mask under a
predetermined pressure while causing a squeegee of a predetermined
length to slide relatively on an upper surface of the metal mask in
a contact fashion.
[0009] In the invention, the squeegee head supplies the paste to
the surface of the metal mask under the predetermined pressure
while causing the squeegee of the predetermined length to slide
relatively on the upper surface of the metal mask in a contact
fashion.
[0010] Consequently, in the invention, compared with the
conventional screen printing apparatus which employs the mesh mask,
a circuit pattern having a large aspect ratio of a sectional shape
is formed by increasing the thickness of the circuit pattern,
thereby making it possible to realize an increase in the conversion
efficiency of a solar cell to be produced.
[0011] According the invention, there is provided a screen printing
apparatus as set forth above, wherein a lower surface of the bridge
portion constitutes a depressed step surface relative to a lower
surface of the covering portion.
[0012] In the invention, the lower surface of the bridge portion
constitutes the depressed step surface, and therefore, the paste is
filled between the substrate and the bridge portion through the
aperture, whereby the belt-shaped circuit pattern can be
formed.
[0013] According to the invention, there is provided a screen
printing method for forming a belt-shaped circuit pattern on a
surface of a substrate comprising the steps of: causing the
substrate to be supported on a support table; placing a metal mask
having a covering portion for covering a part of the surface of the
substrate, a plurality of apertures from which a part of the
substrate is exposed and bridge portions provided individually
between the apertures along a direction which intersects a
longitudinal direction of the circuit patterns on a surface of the
substrate; and supplying a paste to be the circuit pattern to a
surface of the metal mask under a predetermined pressure by a
cartridge-type squeegee head while causing a squeegee of a
predetermined length to slide relatively on an upper surface of the
metal mask in a contact fashion.
[0014] In this invention, the squeegee head supplies the paste to
the surface of the metal mask under the predetermined pressure
while causing the squeegee of the predetermined length to slide
relatively on the upper surface of the metal mask in a contact
fashion.
[0015] Consequently, in the invention, compared with the
conventional screen printing apparatus which employs the mesh mask,
a circuit pattern having a large aspect ratio of a sectional shape
is formed by increasing the thickness of the circuit pattern,
thereby making it possible to realize an increase in the conversion
efficiency of a solar cell to be produced.
Advantageous Effects of the Invention
[0016] According to the screen printing apparatus and the screen
printing method of the invention, the squeegee head supplies the
paste to the surface of the metal mask under the predetermined
pressure while causing the squeegee of the predetermined length to
slide relatively on the upper surface of the metal mask in a
contact fashion.
[0017] By adopting this configuration, according to the screen
printing apparatus and the screen printing method of the invention,
there is provided an advantageous effect that compared with the
conventional screen printing apparatus which employs the mesh mask,
a circuit pattern having a large aspect ratio of a sectional shape
is formed by increasing the thickness of the circuit pattern,
thereby making it possible to realize an increase in the conversion
efficiency of a solar cell to be produced.
DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a front view of a screen printing apparatus having
an open-type squeegee to which a screen printing method according
to an embodiment of the invention is applied.
[0019] FIG. 2 is a front view of a screen printing apparatus having
a cartridge-type squeegee to which the screen printing method in
FIG. 1 is applied.
[0020] FIG. 3 is a side view of the screen printing apparatus in
FIG. 1.
[0021] FIG. 4 is a plan view of the screen printing apparatus in
FIG. 1.
[0022] FIG. 5 is a plan view of a metal mask which is applied to
the screen printing apparatus in FIG. 1.
[0023] FIG. 6 is an enlarged view of the metal mask in FIG. 5.
[0024] FIG. 7 is an enlarged view of a main part of the metal mask
in FIG. 5.
[0025] FIG. 8 is a sectional view taken along the line A-A in FIG.
7.
[0026] FIG. 9 is a sectional view taken along the line B-B in FIG.
7.
[0027] FIG. 10 is a perspective view showing an external appearance
of the periphery of the bridge portion of the metal mask in FIG.
5.
[0028] FIG. 11 is a perspective view showing an external appearance
of the periphery of a bridge portion according to a modified
example to the metal mask in FIG. 5.
[0029] FIG. 12 is a plan view of a main part of a modified example
to the screen printing apparatus in FIG. 1.
[0030] FIG. 13 is a plan view of a modified example to the metal
mask in FIG. 5.
[0031] FIG. 14 is a plan view of another modified example to the
metal mask in FIG. 5.
[0032] FIG. 15 is a plan view of a further modified example to the
metal mask in FIG. 5.
MODE FOR CARRYING OUT THE INVENTION
[0033] Hereinafter, a screen printing apparatus and a screen
printing method according to an embodiment of the invention will be
described by reference to the drawings.
[0034] A screen printing apparatus 10 to which a screen printing
method according to an embodiment of the invention includes a
substrate 11, a support table 12 which supports the substrate 11, a
metal mask 1, a squeegee head 13 for supplying a paste P which
constitutes a circuit pattern to a surface of the metal mask 1
while causing squeegees 14 of a predetermined length to slide
relatively on an upper surface of the metal mask 1 in a contact
fashion, and a cleaning mechanism 15 for cleaning a lower surface
of the metal mask 1.
[0035] As is shown in FIGS. 1, 2, 3 and 4, in the screen printing
apparatus 10, the support table 12, which is a positioning means
for positioning a substrate 11, is made up of a Y-axis table 16, an
X-axis table 17 and a .theta.-axis table 18 which are stacked one
on another. In addition, a first Z-axis table 19 and a second
Z-axis table 20 are stacked further on those tables to work in
combination therewith.
[0036] The first Z-axis table 19 has a horizontal base plate 21,
and a substrate 11, which is a printing target, is carried while
being supported at both end portions by two carrier rails 23 which
are disposed in parallel with a substrate carrying direction (an X
direction) at a substrate carrier portion 22 on the base plate 21.
The base carrier portion 22 extends to an upstream side and a
downstream side, and a substrate 11 which is carried in from the
upstream side is carried by the base carrier portion 22 and is
further positioned by the support table 12. The substrate 11 on
which a required printing has been executed is carried out to the
downstream side by the carrier rails 23.
[0037] The metal mask 1 is stretched to be deployed in a mask frame
2. The squeegee head 13 is disposed above the metal mask 1. The
squeegee head 13 is of an open type, and a squeegee lifting
mechanism 25 is provided on a horizontal plate 24 for lifting up or
down the squeegees 14 of the predetermined length. The squeegee
head 13 supplies a paste (refer to FIG. 10) P which constitutes a
circuit pattern to a surface of the metal mask 1 under a
predetermined pressure, and when the squeegee lifting mechanism 25
is driven, the squeegees 14 are lifted down to be brought into
abutment with an upper surface of the metal mask 1.
[0038] FIG. 2 shows a screen printing apparatus 10 which is
equipped with a cartridge-type squeegee head 13 in place of the
open-type squeegee head 13. As in the aforesaid screen printing
apparatus 10, in this printing apparatus 10, too, the squeegee head
13 supplies a paste (refer to FIG. 10) P which constitutes a
circuit pattern to a surface of a metal mask 1 under a
predetermined pressure. Then, when a squeegee lifting mechanism 25
is driven, a squeegee 14 is lifted down to be brought into abutment
with an upper surface of the metal mask 1. The cartridge-type
squeegee head 13 is superior in filling performance to the
open-type squeegee head 13.
[0039] Brackets 27 are provided on vertical frames 26, and guide
rails 28 are provided individually on the brackets 27 so as to
extend in a Y direction. Sliders 29, which are fitted individually
on the corresponding guide rails 28 in a slidable fashion, are
connected to corresponding ends of the plate 24, whereby the
squeegee head 13 is slidable in the Y direction.
[0040] In the cleaning mechanism 15, a cleaning head unit 30 moves
together with a camera head unit 31 for capturing images of the a
substrate 11 and the metal task 1. The camera head unit 31 includes
a substrate recognition camera 32 for capturing an image of a
substrate 11 from thereabove and a mask recognition camera 33 for
capturing an image of the metal mask 1 from a lower surface side
thereof and can recognize a substrate 11 and the metal mask 1
simultaneously when the camera head unit 30 moves.
[0041] Provided on the cleaning head unit 30 are a paper roll 34
around which non-used cleaning paper is wound, a paper roll 35
around which used cleaning paper is wound, and a cleaning nozzle 36
which sets a cleaning area of a predetermined length on a lower
surface of the metal mask 1. The cleaning head unit 30 is supported
on a head X-axis table 38 which is slidably assembled to guide
rails 37 on the vertical frames 26 so as to be moved horizontally
in the Y direction by a head X-axis moving mechanism 39 on the head
X-axis table 38.
[0042] When in a waiting position, the cleaning head unit 30 is
withdrawn to a side of the support table 12. When executing a
cleaning operation, the cleaning head unit 30 is caused to advance
to a position below the metal mask 1 together with the camera head
unit 31, and following this, the cleaning head unit 30 is caused to
rise. Then, the cleaning head unit 30 is moved horizontally in such
a state that the non-used cleaning paper is pressed against the
lower surface of the metal mask 1 by the cleaning nozzle 36,
whereby a cleaning operation is executed.
[0043] Next, the metal mask 1 will be described in detail. As is
shown in FIGS. 5, 6, 7, 8, 9 and 10, the metal mask 1 has, for
example, a thickness dimension T1 of 0.1 mm, a width dimension L1
of 550 mm and a length dimension L2 of 650 mm. The metal mask 1 has
a covering portion 3 which is provided inside the mask frame 2 for
covering a part of a surface of a substrate 11 and a plurality of
rectangular apertures 4 from which a part of the substrate 11 is
exposed. The metal mask 1 also has bridge portions 5 which are
provided between the apertures 4 so as to extend along a direction
which intersects a longitudinal direction of a circuit pattern to
be formed. The metal mask 1 has a plurality of grid portion 6 where
the apertures 4 and the bridge portions 5 are provided and which
are arranged parallel to each other. The metal mask 1 also has
belt-shaped bus-bar portions 7 which are continuous with terminal
end apertures 4 at longitudinal end portions of the grid portions
6.
[0044] There are provided 67 grid portions 6 which each have a line
width of 0.08 mm, for example. The bus-bar portions 7 each having a
width dimension L6 of 2 mm are disposed within a width dimension L3
of 153 mm in the longitudinal direction of the grid portions 6 in
positions lying 39 mm away from the left and right ends of the grid
portions 6 with central portions having a width dimension L4 of 75
mm disposed therebetween. The aperture 4 has a width dimension L7
of 0.08 mm, for example. The bridge portion 5 has a width dimension
L8 of 0.05 mm, for example, and a height dimension L9 of 0.02 mm,
for example. In addition, the bridge portion 5 has a height
dimension L9 of 0.02 mm, for example, at an end portion of the
aperture 4 having a thickness dimension T1 of 0.1 mm, for example,
and therefore, a lower surface of the aperture 4 is formed into a
depressed step surface relative to a lower surface of the covering
portion 3.
[0045] As is shown in a modified example of a metal mask 1 shown in
FIG. 11, a bridge portion 5 may be disposed at a central portion in
a thickness direction of an aperture 4. In this case, too, a lower
surface of the bridge portion 5 is formed into a depressed step
surface relative to a lower surface of a covering portion 3.
[0046] Next, a solar cell electrode forming system to which the
screen printing apparatus 10 is applied and a solar cell electrode
forming method to which the screen printing method is applied will
be described. In the solar cell electrode forming method, a screen
printing step in which the cartridge-type squeegee head is used and
a calcining step are performed.
[0047] In the screen printing step, when a substrate 11 is carried
in to a printing position by the substrate carrier portion 22, the
second Z-axis table 20 is driven so that a lower surface of the
substrate 11 is supported from therebelow. Then, in this state, the
substrate 11 is registered with the metal mask 1 by the support
table 12, and the metal mask 1 is brought into face contact with an
upper surface of the metal mask 1. As this occurs, the squeegee
head 13 disposes the squeegee 14 relative to the metal mask 1 so
that a longitudinal direction of the squeegee 14 follows a
direction which is at right angles to the direction in which the
apertures 4 and the bridge portions 5 are arranged in the metal
mask 1. Then, when the squeegee 14 is caused to slide in the Y
direction relative to the metal mask 1 along the direction in which
the apertures 4 and the bridge portions 5 are arranged while a
paste is being supplied on the metal mask 1 under a predetermined
pressure which is applied by the squeegee 14, an on-contact
printing is performed with the substrate 11 kept in contact with
the metal mask 1. As this occurs, the paste P is filled
sufficiently into the apertures 4 including portions lying below
the bridge portions 5 by being pushed into the portions lying below
bridge portions 5 under pressure from the apertures 4 as the
squeegee 14 moves in the Y direction. The substrate 11 on which the
printing is completed is carried out to the calcining step on the
downstream side by the carrier rails 23.
[0048] Namely, as is shown in FIG. 7, the squeegee head 13 disposes
the squeegee 14 relative to the metal mask 1 so that the
longitudinal direction of the squeegee 14 follows the direction
which is at right angles to the direction in which the apertures 4
and the bridge portions 5 are arranged in the metal mask 1. Then,
when the squeegee 14 is caused to slide in the Y direction relative
to the metal mask 1 along the direction in which the apertures 4
and the bridge portions 5 are arranged while the paste is being
supplied on the metal mask 1 under the predetermined pressure which
is applied by the squeegee 14, the on-contact printing is performed
with the substrate 11 kept in contact with the metal mask 1.
[0049] The paste P is pushed into the portions lying below the
bridge portions 5 under pressure from the apertures 4 by being
supplied to the surface of the metal mask 1 under the predetermined
pressure by the cartridge-type squeegee head 13, whereby the paste
P is filled sufficiently into the apertures 4 including the
portions lying below the bridge portions 5.
[0050] Next, the calcining step, calcining is executed in such a
state that the paste P is placed on the surface of the substrate 11
while being formed into a predetermined shape. By calcining the
paste P in that way, the paste P is formed into an electrode for a
solar cell. As this occurs, by employing the cartridge-type
squeegee head 13 in the screen printing step to form the electrode,
the screen printing step and the calcining step are each performed
once. Then, by employing the cartridge-type squeegee head 13 in the
screen printing step, the electrode is formed in which an aspect
ratio of a sectional shape is set to be not less than 1.0.
[0051] When cleaning is performed in the screen printing apparatus
10 in which printing is completed, a longitudinal direction of the
cleaning nozzle 36 of the cleaning head unit 30 is disposed
parallel to a longitudinal direction of the bus-bar portion 7 of
the metal mask 1, and a lower surface of the metal mask 1 is
cleaned.
[0052] As this occurs, the longitudinal direction of the cleaning
nozzle 36 is disposed parallel to the longitudinal direction of the
bus-bar portion 7 of the metal mask 1. Namely, since the bus-bar
portion 7 is wider than the grid portion 6, an amount of residual
paste on the bus-bar portion 7 is larger than an amount of residual
paste on the grid portion 6. Because of this, by taking the nozzle
disposition which gives priority to cleaning of the bus-bar portion
7 rather than to cleaning of the grid portion 6, the cleaning
quality of the metal mask 1 can be increased in whole.
[0053] As is shown in FIG. 12, in a modified example of a screen
printing apparatus 10, a metal mask 1 is employed in which bridge
portions 5 are provided along a direction which intersects a
longitudinal direction of a circuit pattern which is formed between
apertures 4. A squeegee 14 is disposed relatively to the metal mask
1 so that a longitudinal direction of the squeegee 14 follows a
direction which intersects a direction which is at right angles to
a direction in which the apertures 4 and the bridge portions 5 are
arranged at a predetermined angle .theta.1, and the squeegee 14
moves relatively along an X direction which is at right angles to
the direction in which the apertures 4 and the bridge portions 5
are arranged. By moving the squeegee 14 from the direction which
intersects the direction which is at right angles to the direction
in which the apertures 4 and the bridge portions 5 are arranged at
the predetermined angle .theta.1, the paste P is pushed obliquely
downwards towards portions lying below the bridge portions 5 from
the apertures 4 under pressure, whereby the paste P is filled
sufficiently into the apertures 4 including the portions lying
below the bridge portions 5.
[0054] As is shown in FIG. 13, a modified example of a metal mask 1
has apertures 4 each having a parallelogram shape and arranged
along a longitudinal direction of a circuit pattern to be formed.
Because of this, bridge portions 5 are disposed inclined relative
to a direction which is at right angles to the longitudinal
direction of the circuit pattern to be formed. In this modified
example, a squeegee 14 is disposed relatively to the metal mask 1
so that a longitudinal direction of the squeegee 14 follows a
direction which is at right angles to a direction in which the
apertures 4 and the bridge portions 5 of the metal mask 1 are
arranged. Then, the squeegee 14 moves relative to the metal mask 1
along an X direction which is at right angles to the direction in
which the apertures 4 and the bridge portions 5 are arranged. By
adopting this configuration, a paste P is pushed from acute angle
portions of the bridge portions 5 which are disposed inclined
relative to the traveling direction of the squeegee 14 towards
portions lying below the bridge portions 5 under pressure, whereby
the paste P is filled sufficiently into the apertures 4 including
the portions lying below the bridge portions 5. In addition, the
squeegee 14 may move relative to the metal mask 1 in a Y direction
which follows the direction in which the apertures 4 and the bridge
portions 5 are arranged.
[0055] As is shown in FIG. 14, another modified example of a metal
mask 1 has apertures 4 each having an isosceles trapezoidal shape
and arranged along a longitudinal direction of a circuit pattern to
be formed in such a way that an upper base of a trapezoidal
aperture 4 follows a lower base of an adjacent one or a lower base
of a trapezoidal aperture 4 follows an upper base of an adjacent
one in an alternate fashion. Because of this, bridge portions 5 are
disposed inclined relative to a direction which is at right angles
to a longitudinal direction of the circuit pattern to be formed. In
this modified example, a squeegee 14 is disposed relatively to the
metal mask 1 so that a longitudinal direction of the squeegee 14
follows a direction which is at right angles to a direction in
which the apertures 4 and the bridge portions 5 of the metal mask 1
are arranged. Then, the squeegee 14 moves relative to the metal
mask 1 along the direction in which the apertures 4 and the bridge
portions 5 are arranged. By adopting this configuration, a paste P
is pushed from acute angle portions of the bridge portions 5 which
are disposed inclined relative to the traveling direction of the
squeegee 14 towards portions lying below the bridge portions 5
under pressure, whereby the paste P is filled sufficiently into the
apertures 4 including the portions lying below the bridge portions
5. In addition, the squeegee 14 may move relative to the metal mask
1 in a Y direction which follows the direction in which the
apertures 4 and the bridge portions 5 are arranged.
[0056] As is shown in FIG. 15, a further modified example of a
metal mask 1 has square apertures 4 along a longitudinal direction
of a circuit pattern to be formed. In this modified example, a
squeegee 14 is disposed relatively to the metal mask 1 so that a
longitudinal direction of the squeegee 14 follows a direction which
intersects a direction which is at right angles to a direction in
which the apertures 4 and bridge portions 5 of the metal mask 1 are
arranged at a predetermined angle. Then, the squeegee 14 moves
relatively along an X direction which is at right angles to the
direction in which the apertures 4 and the bridge portions 5 are
arranged of the metal mask 1. By adopting this configuration, a
paste P is pushed in from the apertures 4 into portions lying below
the bridge portions 5 under pressure as the squeegee 14 moves in
the X direction, whereby the paste P is filled sufficiently into
the apertures 4 including the portions lying below the bridge
portions 5.
[0057] Thus, as has been described above, according to the screen
printing apparatus 10 according to the embodiment of the invention,
the squeegee head 13 supplies the paste to the surface of the metal
mask 1 under the predetermined pressure while causing the squeegee
14 of the predetermined length to slide on the upper surface of the
metal mask 1 in the contact fashion.
[0058] Consequently, according to the screen printing apparatus 10
according to the embodiment of the invention, compared with the
conventional screen printing apparatus which employs the mesh mask,
by employing the cartridge-type squeegee head 13 in the screen
printing step, the thickness of the circuit pattern formed is
increased so that the circuit pattern formed can have a large
aspect ratio of a sectional shape thereof, thereby making it
realize an increase in the conversion efficiency of a solar cell to
be produced.
[0059] According to the screen printing apparatus 10 according to
the embodiment of the invention, the lower surface of the bridge
portion 5 is formed into the depressed step surface, and therefore,
the paste is filled between the substrate 11 and the bridge
portions 5 through the apertures 4, thereby making it possible to
form the belt-shaped circuit pattern.
[0060] According to the screen printing method according to the
embodiment of the invention, the squeegee head 13 supplies the
paste to the surface of the metal mask 1 under the predetermined
pressure while causing the squeegee 14 of the predetermined length
to slide on the upper surface of the metal mask 1 in the contact
fashion.
[0061] Consequently, according to the screen printing method
according to the embodiment of the invention, compared with the
conventional screen printing method which employs the mesh mask, by
employing the cartridge-type squeegee head 13 in the screen
printing step, the thickness of the circuit pattern formed is
increased so that the circuit pattern formed can have a large
aspect ratio of a sectional shape thereof, thereby making it
realize an increase in the conversion efficiency of a solar cell to
be produced.
EXAMPLE
[0062] Next, an example will be described which was made in order
to verify the function and advantage of the screen printing
apparatus 10 and the screen printing method to which the solar cell
electrode forming system according to the invention is applied. In
this example, a comparison example 1 and a comparison example 2
were prepared to form electrodes for a solar cell. In the
comparison example 1, a mesh mask having a mesh aperture of 50% or
lower was used, and gap printing or off-contact printing was
performed by use of the open-type squeegee head, and in the
comparison example 2, a mesh mask having a mesh aperture of 50% or
lower was used, and on-contact printing was performed by use of the
cartridge-type squeegee head. Then, aspect ratios of sectional
areas based on height dimensions and width dimensions of the
electrodes formed were measured.
[0063] The results of the measurements show that the aspect ratio
of the comparison example 1 was 0.3 or smaller and the aspect ratio
of the comparison example 2 was 0.7 or smaller. In contrast to
these aspect ratios of the comparison examples, the aspect ratio of
the invention was 1.0 or larger. This is because the squeegee 14 of
the cartridge-type squeegee head 13 which is disposed relatively to
the metal mask 1 so that the longitudinal direction thereof follows
the direction which is at right angles to the direction in which
the apertures 14 and the bridge portions 5 of the metal mask 1 are
arranged is moved relatively to the metal mask 1 along the
direction in which the apertures 4 and the bridge portions 5 are
arranged. This enables even a metal mask 1 having a mesh aperture
of 90% or larger to be adopted.
[0064] The invention is not limited to the support table 12, the
squeegee 14 and the cleaning mechanism 15 which are used in the
embodiment described above, and hence, these constituent members
can be modified as required.
[0065] This patent application is based on Japanese Patent
Application (No. 2010-068254) filed on Mar. 24, 2010, the contents
of which are to be incorporated herein by reference.
DESCRIPTION OF REFERENCE NUMERALS AND CHARACTER
[0066] 1 metal mask; 3 covering portion; 4 aperture; 5 bridge
portion; 10 screen printing apparatus; 11 substrate; 12 support
table; 13 squeegee head; 14 squeegee; P paste.
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